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Date:   Wed, 8 Jul 2020 09:19:06 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     linux-crypto@vger.kernel.org, Martin Willi <martin@strongswan.org>,
        Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: [PATCH] crypto: x86/chacha-sse3 - use unaligned loads for state
 array
Message-ID: <20200708161906.GA4557@sol.localdomain>
References: <20200708091118.1389-1-ardb@kernel.org>
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On Wed, Jul 08, 2020 at 12:11:18PM +0300, Ard Biesheuvel wrote:
> Due to the fact that the x86 port does not support allocating objects
> on the stack with an alignment that exceeds 8 bytes, we have a rather
> ugly hack in the x86 code for ChaCha to ensure that the state array is
> aligned to 16 bytes, allowing the SSE3 implementation of the algorithm
> to use aligned loads.
> 
> Given that the performance benefit of using of aligned loads appears to
> be limited (~0.25% for 1k blocks using tcrypt on a Corei7-8650U), and
> the fact that this hack has leaked into generic ChaCha code, let's just
> remove it.
> 
> Cc: Martin Willi <martin@strongswan.org>
> Cc: Herbert Xu <herbert@gondor.apana.org.au>
> Cc: Eric Biggers <ebiggers@kernel.org>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Reviewed-by: Eric Biggers <ebiggers@google.com>